1. Field of the Invention
The present invention relates in general to secondary electrolytic cells, and, more particularly, to rechargeable lithium cells having an electrode constructed with a graphite material.
2. Background Art
Rechargeable, or secondary lithium cells, have been known in the art for several years. Furthermore, lithium cells which utilize an electrode constructed with a carbon material have likewise been known in the art.
Although such carbon materials, and, in particular, graphite carbon materials, have proven to be beneficial in lithium cells --inasmuch as they provide long cycle life and high energy levels over other existing materials--they nonetheless have some known thereoretical limitations. For example, in an electrolytic cell having a lithium source electrode and an electrode constructed with graphite particles, the known theoreticle capacity of LiC.sub.6 is 372 mAh/g. While testing has been done in the field to develop a carbon/graphite electrode for use in a lithium cell which will have a reversible capacity close to that for LiC.sub.6, such testing has yet to achieve such a goal. (See, e.g. Development of a High Energy Density Rechargeable Lithium -Ion Cell Technology, authored by Walter Ebner, et al., of Rayovac Corporation, Madison, Wi., presented at the 36th Power Sources Conference in Cherry Hill, New Jersey Jun. 6-9, 1994).
Furthermore, while such testing and advancements in the prior art have resulted in the development of lithium cells having greater energy densities, and, in turn, greater run time, the reversible capacity of the cells, developed to date, typically decrease over several initial succeeding charge and discharge cycles until a relatively stabilized capacity has been obtained--again, at a reversible capacity well below 372 mAh/g. Accordingly, it is an object of the present invention to provide an electrolytic cell using small particle graphite wherein the reversible capacity of the graphite is substantially maintained well beyond 372 mAh/g after the initial charge and discharge cycle.
It is also an object of the present invention to provide an electrolytic cell using small particle graphite wherein the reversible capacity of the graphite continues to remain beyond 372 mAh/g after subsequent charge and discharge cycles.
It is still further an object of the present invention to provide an electrolytic cell using small particle graphite wherein the reversible capacity of the graphite is increased beyond the known theoreticle capacity of 372 mAh/g for LiC.sub.6.
These and other objects of the present invention will become apparent in light of the present Specification, Claims and Drawings.